The ulnar nerve is a branch of the medial cord of the brachial plexus and contains branches from the ventral rami of the spinal nerve roots C8 and T1

In the proximal 2/3 of the upper limb, the ulnar nerve runs runs in the medial bicipital groove together with the median nerve and the brachial artery and veins; these neurovascular structures are all sandwiched between the triceps brachii and the biceps brachii muscles – and it is anterior to the medial intermuscular septum

Between the middle and distal 1/3 of the arm, the ulnar nerve pierces the medial intermuscular septum and becomes sandwiched between the triceps brachii muscle posteriorly and the brachialis muscle anteriorly and deviates away from the median nerve and brachial vessels which descend postero-medial to the biceps muscle and anterior to the brachialis muscle

In the most distal part of the arm, the ulnar nerve enters the ulnar groove (or sulcus) on the backside of the medial epicondyle of the humerus, while the median nerve and the brachial vessels run anterior to the medial epicondyle

The ulnar nerve innervates the volar side of the of medial 1 1/2 digits, and it innervates the dorsal side of the medial 2 1/2 digits

At the level of the elbow the median nerve runs medial to the brachial artery

Below the elbow the median nerve descends in the midline without an adjacent artery; it runs under the short head of the biceps brachii muscle and the tendon of the biceps brachii muscle and between the two head of the pronator teres to the forearm

The short head of the biceps brachii muscle and the biceps brachii tendon as well as the pronator teres muscle have been removed in the picture on the right to expose the median nerve

The brachialis muscle is highlighted with orange colour; brachioradial muscle (cyan asterix), long head of the biceps brachii muscle (green asterix)

The median nerve runs in the medial bicipital groove alongside the brachial artery and veins, which is a subcutaneous longitudinal groove that runs medially along the arm

The medial bicipital groove is delineated by the biceps brachii, the brachialis and the medial intermuscular septum (see next page)

Proximally in the bicipital groove, the median nerve is lateral to the brachial artery

Along the course to the cubital fossa the median nerve crosses to the medial side of the artery – usually crossing anterior to the artery

Liebmann O, Price D, Mills C, Gardner R, Wang R, Wilson S & Gray A: Feasibility of forearm ultrasonography-guided nerve blocks of the radial, ulnar, and median nerves for hand procedures in the emergency department. Annals of Emergency Medicine 48:558-562 (2006)

The hyperechoic rounded or oval median nerve is typically superficially located just medial to the pulsatile brachial artery at the level of the elbow crease

Place the patient supine

Place the high-frequency linear probe in the axial plane in the elbow crease

Visualize the pulsatile brachial artery

Locate the hyperechoic cross-sectional view of the median nerve just medial to the brachial artery (see sonoanatomy page)

Insert the needle with in-plane approach from the medial end of the probe

Inject 3-5 mL of local anaesthetic perineurally

At the level of the elbow, the radial nerve has a very characteristic spindle shaped sonographic cross-sectional presentation

Place the patient supine with the forearm externally rotated

Place the high-frequency linear probe in the axial plane at the elbow crease

Visualize the pulsatile brachial artery

Slide the probe laterally and a bit proximal and visualize the radial nerve on top of the lateral humeral epicondyle (see next page)

Insert the needle with in-plane technique either from the medial or the lateral end of the probe

Inject 3-5 mL of local anaesthetic perineurally

The radial nerve can be tracked proximally with ultrasound from the lateral epicondyle to the radial humeral sulcus

The radial nerve becomes an anechoic rounded profile just distal to the radial humeral sulcus